Inadvertent Intraarterial Injection of ¹⁸F-FDG: A Case Report and Literature Review of Hot Forearm and Hot Hand Signs

DISCUSSION

It is well established that an unintentional intraarterial injection of ^99mTc-methylene diphosphonate can produce a hot forearm or hot hand sign characterized by a pronounced soft-tissue uptake distal to the arterial distribution, which is also called the glove phenomenon in some reports (1–4). When the increased ^99mTc-methylene diphosphonate uptake is restricted only to the ipsilateral bones and periarticular regions, it can also mimic a reflex sympathetic dystrophy (5). These phenomena are different from extravascular leakage (9,10).

More serious interferences have been observed when ^99mTc-sestamibi or ²⁰¹Tl-chloride for myocardial perfusion scintigraphy was accidentally injected into the artery (6,7). These kinds of tracers accumulate preferentially in the skeletal muscles, with the region of intense uptake extending from the forearm and hand to the upper arm and even to the shoulder (6). Moreover, the quality of the reconstructed cardiac images deteriorates remarkably as the skeletal muscle absorbs most of the radioactivity.

The incidence of inadvertent intraarterial injection of ¹⁸F-FDG is likely underestimated because the hands and forearms are often not included in the PET/CT images. It might also have been ignored or considered as a leakage of radioactivity in some cases. Usually, when ¹⁸F-FDG is mistakenly injected into a brachial artery, the image quality of PET is still suitable for visual interpretation (11,12). However, the SUVs of the lesions may be underestimated as indicated by the lower SUVs in liver or mediastinal soft tissues, in comparison to other normally injected patients. SUV correction techniques for ¹⁸F-FDG injection with venous leakage or extravasation have been investigated, and a similar technique may be applicable in instances of intraarterial injections (13).

Assessment of risk factors before a venipuncture is important. An intravenous injection for patients referred for a PET/CT scan or a bone scan is sometimes challenging because they may have a history of malignancy and the superficial veins may have shrunk after multiple courses of chemotherapy. In addition, for those patients referred for myocardial scintigraphy, the superficial veins may not be clearly visualized because of the obesity and diabetes that are commonly encountered in these patients. In addition, elderly patients with dehydration or vessel disease are also more prone to accidental arterial puncture. Under these conditions of high risk, an intravenous injection should be performed with care to avoid either accidental intraarterial injection or radioactivity leakage.

A good understanding of the normal anatomy and variations of the vessels is important to avoid an inadvertent intraarterial injection. Taking the antecubital fossa venipuncture as an example, there are 3 main veins commonly used, including the basilic vein, the median cubital vein, and the cephalic vein. The brachial artery and its 2 main branches, the ulnar artery and the radial artery, may run right beneath these superficial veins (14). Under difficult conditions, careful observation of the color and movement of blood return would be helpful to ensure accurate venous access.

After this incident, all our technologists received in-service training from hospital intravenous nurses. The variability of the venous anatomy was discussed; catheter insertion techniques and angles were the main discussion points. Visual assessment after catheter placement was emphasized, as was rechecking before tracer administration. The technologists were enjoined not to administer the tracer if pulsation of the catheter is observed. Also, they were asked to obtain a second opinion if there was uncertainty about the catheter placement. Since the training, we have not had any arterial injections.

In summary, the first-pass effect contributed to a different distribution pattern of a radioactive tracer when it was inadvertently injected into an artery. A tracer that is more susceptible to uptake by the forearm or hand is more likely to produce the hot forearm or hot hand sign. The variation of image pattern is related to the involved artery and its perfusion, as well as the extraction ability of the corresponding tissues for a specific radiotracer. In fact, in radionuclide assessment of peripheral arterial diseases, intraarterial injection of ^99mTc-labeled human serum albumin microspheres was used as a noninvasive method before exercise plus intravenous injection of ^99mTc-sestamibi had been established (15,16).

As reported in many clinical cases, mistaken delivery of certain intravenous medications via arterial access has led to serious sequelae, including paresthesias, severe pain, motor dysfunction, compartment syndrome, gangrene, and even limb loss (17). Although the consequences are much less serious for radionuclide imaging, the personnel who administer the intravenous injections should be aware of this potential problem to minimize its impact.